Synthetic polymeric compositions which are bioerodible and biocompatible have become increasingly important and valuable in recent years. One application for such compositions is as surgically implantable biomaterials or prosthetic articles for human and animal subjects in vivo. Consequently, such biomaterials are articles which serve as implants or prostheses, artificial devices introduced into living tissues to replace a missing part of the body; these are exemplified by articles such as vascular grafts, biodegradable sutures and orthopedic appliances such as bone plates and the like. In order for an implantable or prosthetic article to be truly useful, it should be composed of a synthetic polymeric composition having specific characteristics and properties: First, the synthetic composition should provide sufficient elasticity and tensile strength over a preselected minimal time period which will vary with the specific application. Second, the synthetic composition should be non-immunogenic, biocompatible, biodegradable in vivo and yield degradation products which are themselves non-inflammatory, non-toxic and non-antigenic.
Despite continuing research effort, very few synthetic polymeric biomaterials have been developed which provide all these desired attributes. Presently known biodegradable polymers such as polylactic acid, polyglycolic acid, polycaprolactones and the various polyamides also all lack the desired mechanical strengths over time [Heller et al, "Theory and Practice of Control Drug Delivery from Bioerodible Polymers", in Controlled Release of Bioactive Material, R. W. Baker Editors, Academic Press, New York, 1908, pp. 1-17; Pitt et al, Biomaterials 2: 215-220 (1981); Chu, C. C., J. Appl. Polym. Sci. 26: 1727-1734 (1981)].
Prior to this invention, polyimidocarbonates have been prepared as disclosed in U.S. Pat. No. 3,491,060. However, these polymers have not been commercially used. Specifically, they have not been considered as materials useful for implantable devices.